Process for the direct syntheses of ammonia



March 20, 1934. F. c. REED PROCESS FOR THE DIRECT-SYNTHESES 0F AMMONIAFil ed'April 3. 1931 .2 Sheets-Sheet 1 BY g ATTORNEYS.

March 20, 1934.

1?. Sheetseet IN VENTOR,

Filed April 3, 1931 Tar/'65} 6. Pea.

000 00000ud 000000 OOBO 000fl0000000 llllllllllllllllllll llllllllll l-A1] ORNEYJ Patented- Mar. 20, 1934 1,952,031 PROCESS FOR THE manorSYNTHESES OF AMMONIA Forrest C. Reed, Kansas City, Mo. Application April3, 1931, Serial No. 527,396

26 Claims.

The present invention relates to processes for the direct synthesis ofammonia, and particularly to improvements in such processes involvingthe direct synthesis of ammonia from its elements, nitrogen andhydrogen, by passing said elements, mixed in the proper proportions,

over a suitable catalyst at elevated temperatures and pressures, andwhen said elements contain a high initial precentage of inert gases,such as argon and methane.

In the art of producing ammonia with hydrogen obtained from water gasand nitrogen obtained from producer gas, there are present, in theinitial gas mixture, inert gases such as argon and met ane, the volumeas given on page 113 of the eport on Fixation and Utilization ofNitrogen y Nitrate Division of the Ordnance Office, Unit States WarDepartment, is from 0.5% to 1.0% of the entire gas mixture. These inertgases accumulate in the apparatus until further accumulation wouldresult in retarding production at which time they must be purged with aresulting loss of hydrogen-nitrogen gas, the loss depending on theconcentration of said inert gases in the system, from which they arepurged. I

In the production of ammonia with hydrogen obtained from coke oven gasor from the cranking of natural gas, where the percentage of methane isconsiderably over one per cent liquefaction of all the gases is resortedto in order to remove methane and other impurities. Equipment for thisliquefaction is complicated and expensive. Furthermore, in producinghydrogen by cracking the hydrocarbons of natural gas, it iscomparatively easy and economical to crack the gas to carbon andhydrogen having 5% of uncracked methane, while it is extremely diificultand expensive to crack to carbon and hydrogen having as .low as 1%methane.

Advantages also reside in not cracking natural gas to completion becauseof the extremely high temperatures and long time of contact requiredwhich diminishes the value of the by-product carbon black; whilecracking to the order of 5% of methane in the resulting gas mixture, asatisfactory grade of carbon black is produced.

Where ammonia is produced from water gas hydrogen and where the inertsin the initial gas mixture amount to as much as 1.0% methane and withthe usual concentration of 10% in the circulatory system, the purge losswould be approximately of the gas mixture which in most cases would bepermissible.- If, however, the, inerts in the initial gas mixture wereof the order of 5% as in the use of hydrogen from natural gas, the purgeloss would be of the gas mixture which would not be permissible. It is,therefore, obvious when producing ammonia from a hydrogen-nitrogengas'mixture having a high initial percentage of inert gases, that unlessliquefaction of all the gases is resorted to for removing inerts, thensuitable means must be provided to increase the concentration of inertgas in the circulatory system to a degree where purging becomeseconomical.

The primary object of the present invention is, therefore, to providemeans for increasing the concentration of inert gas in the circulatorysystem, thereby reducing the loss of hydrogen and nitrogen when purgingoif inert gases and impurities, and permitting also the use of ahydrogen-nitrogen gas mixture having a high initial percentage of inertgases such as argon and methane; to provide means for maintainingsubstantally constant pressure of operation; to provide means forpurification of the. gas mixture; to provide improved disposition ofcatalytic body and direction of flow of gases; and to obtain fiexibilityof operation.

In order to obtain the foregoing and other advantages as may be broughtout inthe accompanying specifications and drawings, it is proposed tooperate, in combination with each other, two complete systems ofconverters. One system of converters concentrates the inert gases to adegree economical with the desired production of ammonia and the othersystem of converters further concentrates the inerts to a degreeeconomical for the purging of inert gases. Part of the gases arerecirculated through the first system of converters, and part of thegases, leaving the first system of converters, are circulated throughthe second systemof converters. The first system of converters ishereinafter referred to as the primary system while the second system of.convert ers is designated the secondary system. Either of said systemsmay consist of one or more converteYs. The primary system preferablyconsists of two converters; this especially where the make-up gascontains small amounts of impurities other than inert gases, such asoxygen, the oxides of carbon, and sulphur from lubricating .oils inwhich case the first converter acts as a purifier, the catalystretaining such poisons as sulphur and the oxides reacting from hydrogento form methane and water. The water is removed with the liquid ammoniawhen the ammonia is condensed after the converter. Little or no ammoniamight be formed in the first converter depending on the amounts ofimpurities present. If no ammonia is formed in first converter, theammonia for absorbing impurities can be sup plied in any suitable mannersuch as condensing the ammonia from the recirculated gas from thesucceeding converters. The secondary system preferably consists of asingle converter, the gas being either recirculated or passed throughthe converter but once and then allowed to escape.

In my United States Letters Patent No. 1,639,272 dated August 16, 1927,for Processes for the direct synthesis of ammonia, Ihave disclosedfigures indicating approximately the advantages of the series cyclicprocess over former cyclic processes, especially for reaching highconcentrations of inerts. The importance of temperatures, spacevelocities, and catalyst promoters on the efficiency of ammoniaconversion is given on pages 21 to 29 inclusive of Contributions to theStudy of Ammonia Catalysts from the U. S. Fixed Nitrogen ResearchLaboratory, reprinted from Chemical and Metallurgical Engineering,volume 26, Nos. 11, 12, 13, 14 and 15 March 15, 22 and 29, and April 5and 12, 1922. For example:

A catalyst operating at 510 C. on gas containing.

0.082% of poisons will have the same eificiency as when operatingon'pure gas at 430 C. A catalyst operating on gas containing 0.10% ofpoisons will have the same efiiciency at 5000 .space velocity as withonly 0.02% of poisons at 20,000 space velocity. A catalyst having a highefiiciency on pure gas will have a low efficiency on impure gas while acatalyst having a low efiiciency on pure gas will have a high efficiencyon impure gas. Furthermore, the higher the conversion and therefore themore ammonia formed and removed with each passage of the gases over thecatalyst, the higher will be the concentration of inert gases left withthe unconverted hydrogen and nitrogen gases. The lower the coolingtemperature after each converter the more ammonia removed and thereforethe higher the concentration of inert gas remaining in the unconvertedgases. If only a single converterwere used as in the Haber (UnitedStates Letters Patent Number 1,202,995 dated October 31, 1916) cyclicprocess operating in conjunction with another plant such as an ammoniumsulphate'plant where the expanded ammonia ,used in cooling is useddirectly to neutralize sulphuric acid, it would not be practical to coolbelow -10 C. where the pressure of the expanded ammonia would correspondto the back pressure on the sulphate saturator.

In the process contemplated by the present invention, cooling after theconcentrating converter can be carried to 50 C. by using ammoniacompressors and recondensing the ammonia used for cooling whilethe'cooling after the first converters. can be regulated separately tosuit the plant operation.

This process then permits for each converter, a catalyst, operatingtemperature, cooling temperature, and space velocity most suitablefor/each step in the process, i. e., for the removal of small amounts ofpoisons in the make-up gas, for the maximum production of ammonia, andfor maximum concentrations of inert gases.

The accompanying drawings illustrate apparatus embodying the'salientfeatures of the invention and through the use of which the novel processmight be performed.

Figure 1 is a diagrammatical showing of apparatus adaptable for carryingout the process of the present invention, and V Figure 2 is a verticalcentral section of a converter forming one of the units of the system.

Like reference characters designate similar parts throughout the viewsand A and A of Figure 1 are primary converters operating in a seriescyclical system wherein is interposed circulating pump P. A" is asecondary converter operating in a separate cyclic system havingcirculating pump P andutilizi'ng part of the unconverted gas leavingconverter A. M, M, and M" are condensers. N, N, and N are liquid ammoniareceivers of well known construction.

Referring to Figure 2, C is a cylindrically formed pressure sustainingvessel, D and D are catalytic materials, J is the outer wall of thecatalytic chamber in which the wall K divides the catalytic mass into aninner and an outer body.

The catalyst chamber J is filled with suitable catalyst D and D and issupported by suitable means such as by bolts p to cover 1). The wall Kcould be either straight or preferably tapering sonically as shown.Dividing the catalytic mass in this manner makes it possible toproportion the volumes of the two parts in such a manner that the heatgenerated by reaction is equalized and for reasons of strength thecooler part of the catalytic mass is nearest the walls of the pressuresustaining vessel C. E is a heat exchanger of suitable design, hereshown as a plurality of spirally-wound tubes E, two or more tubes beingwound together similar to a multiple threaded screw thread andcommunicatively connected to narrow passage H at h and to outletconnection 9 at h. The cylindrically formed walls 8 and :1 form thenarrow passage H communicating at bottom with inner catalyst body at Wand with heat exchanger E at h. G and G are holes through upper andlower ends respectively of the catalytic chamber for depositing andremoving catalyst. I is a cylindrically formed shell closed at bottomforming a dead space between itself and catalyst chamber and a narrowspace between itself and the wall of pressure sustaining vessel C. Thepressure within the apparatus is equalized bysuitable .openings V. Thespace enclosing heater F is communicatively joined to outer catalystspace by passage 1' formed at the bottom of the catalyst chamber.

Theprocess may be carried out in the following manner: Hydrogen andnitrogen gas mixed in the proper proportions are supplied at m in Fig.l, the flow through the system being in the direction of the arrows. Theflow through converters A, A, and A" can be seen by referring to Fig. 2.Electric current is supplied at C to heater F and a small amount ofhydrogen and nitrogen gas of the proper mixture is admitted at f andpassed through the converter in the direction of arrows and out at gwhile the temperature of. the catalyst is brought up to reactiontemperature. The pressure of the apparatus is then gradually .increasedto the operating pressure.

The gas entering at j is conducted downwardly over the outside of tubesE of heat exchanger E, through holes 1" to space surrounding heater F,from thence through passage r at bottom of catalyst chamber to the outercatalytic body D where the flow is upward to the top and then downwardly through inner catalytic body D, through holes W to narrow passageH, then flowing upthe heat of reaction is -scribed for converter A, allor system of converter A" wardly into the inside of heat exchanger tubesE at h and out at h into outlet g. The ingoing gases are thus heated bythe outgoing gases and usually suflicient to make the processautothermal in'which case the electric heater is used only in startingthe reaction. The reaction could as well be started by external heatingof the gases. In order to control the heat exchange, part or all of thegases could be 'admitted at bottom of converter by manipulation ofvalves a and b, the gases passing upwardly between cylindrical shell Iand wall of pressure sustaining vessel C, through holes V and over heatexchanger as before. 4

Referring to Fig. 1, the mixture of hydrogen and nitrogen gas has passedthrough converter A of the primary system as above described, anypoisons present, suchas sulphur, have been absorbed by the catalyst andany oxygen or the oxides of carbon present have reacted with hydrogen toform methane and water, and part of the hydrogen-nitrogen mixture hasbeen converted to ammonia gas. All of these gases are now conductedthrough pipe g to condenser M where they are cooled and the-ammonialiquefied and collected in the receiver N. Any water present is removedwith the liquid ammonia. The liquid contents of receiver N is removedthrough pipe 21 extending below the surface of the liquid so that theoperating pressure forces the liquid ammonia out. The unconverted gasesnow purified except for the inert gases present are then conductedthrough pipe 1: to converter A where the procedure through the converteris the same as depart of the gas passing through valve 0. to top ofconverter or through valve b to bottom of converter.-

A portion of the gas leaving receiver N through pipe :12 ,isrecirculated with the fresh make up gas entering at m through primaryconverters A and A by means of circulating pump 1?, and the remainingportion of the gas leaving receiver N is circulated through the separatesecondary syste of converter A by means of circulating pump in the samemanner as described for converter A. The volume of gas passing througheither system is preferably and e and by the speed of circulating pumpsP and P". The inert gas is allowed to accumulate in the system ofconverters A- and A to a degree of concentration permissible with thedesired production of ammonia. In order not to further increase thedegree of concentration of inerts in converters A and A of the primarysystem, a volume of gas, sufficient at this degree of concentration tocarry inert gas, equal in volume to the inerts entering the primarysystem with the make up gas at m; must passinto thesecondary where theconcentration is further increased to a. degree where purging becomeseconomical and then the secondary system is continuously purged throughvalve S. The primary system'can be purged through valve S if desired.The purged gas can be used as fuel in gas engines or otherwise disposedof. In order to equalize conversion in converters A and A and otherwisecontrol operation, part of gas in primary system can be by-passed at n.

The catalyst, space velocity, operating temperature, and degree ofcooling would be to suit the operating conditions in each converter.Conyerter-A, to withstand the poisoning efiect of the impurities in thegas, should preferably have a rugged catalyst andi operate atcomparatively high temperature and low space velocity.

controlled by valves d tively high space velocity for maximumproduction. The cooling after conversion should be as low as permissibleconsidering the disposition of the vaporized ammonia used in cooling.Con verter A", to oifset the reduction of conversion due to the partialpressure of inert gas at high concentration, would have preferably acatalyst to operate at comparatively low temperature and space velocityand the cooling after conversion would be preferably by a two stagerefrigeration machine with vacuum on suction to give coolingtemperatures of the order of 40 0., all of which tends to increase theamount of ammonia formed and removed with each passage of the gases overthe catalyst and thereby increasing the concentration of inertsremaining in the gas.

Besides the advantage of suitable catalyst,

space velocities, operating temperatures and cooling temperatures foreach-converter of the primary and secondary system, the operatingpressure of secondary system can be boosted to a pressure at least ashigh as or even higher than the operating pressure of converter A of theprimary system whichtends to further increase conversion in secondarysystem and thereby increasing the concentration of inerts. The operatingpressure of an ammonia process is usually considered as substantiallyconstant, yet through two converters there would be an drop in pressurewhich can be compensated for by the process of the presentinvention. Afurther advantage is the use of converter A as a V which percirculatingermore the size of piping, condensers and circulating pumps of thepresent invention are materially reduced because of the reduced volumeof recirculated gas.

While the apparatus shown in Fig. 1, has two converters in the primarysystem and one converter in the secondary system yet either system couldas well consist of two or more converters without departing from thespirit and scope of the present invention. It is also possible tocombine one secondary concentrating system with two ormore primarysystems. Furthermorethe circulating pump P" of the secondary systemcould as well be used to boost the operating sure of secondary system toa pressure much higher than that thereby increase the conversion to suchan extent that the residual. gases leaving,secondary system could eitherall be purged after the removal of ammonia and without furthercirculation, or recirculated by throttling with valve 1'.

Obviously there'are other methods of carrying out the present inventiontherefore I don'ot wish of the primary system and 110 appreciable ing amixture of hydrogen required by the following claims when construed inthe light of the prior art.

Having thus described the invention, what is claimedas new and desiredto be secured by Letters Patent is:

1. The process of producing ammonia by passand nitrogen over a suitablecatalytic agent at elevated temperature and pressure and removing at alower temperature the ammonia formed then again passing a portion of theresidual gases over the same catalytic agent, while repeatedly passinganother portion over a second catalytic agent in like manner, andremoving at lower temperature, after each catalytic agent, the ammoniaformed by each passage of gases over said catalytic agent and replacingthe quantity of gases removed, with fresh hydrogen and nitrogen suppliedto said first catalytic agent.

2. The process of producing ammonia by passing a mixture of hydrogen andnitrogen over a suitable catalytic agent at elevated temperature andpressure and removing at a lower temperature the ammonia formed thenagain passing a portion of the residual gases over the same catalyticagent, while repeatedly passing the remaining portion over a secondcatalytic agent in like manner, and removing at lower temperature, aftereach catalytic agent, the ammonia formed by each passage of gases oversaid catalytic agent and replacing the quantity of gases removed, with.fresh hydrogen and nitrogen supplied to said first catalytic agent andwhile purging continuously from a point after ammonia has been removedfrom said second catalytic agent.

3. The process of producing ammonia by passing a. mixtureof hydrogen andnitrogen, after heat exchange with the gases of reaction and at elevatedtemperature and pressure, over a catalytic agent and removing at lowertemperature the ammonia formed then again passing a portion of theresidual. gases over same catalytic agent, while repeatedly passing theremaining portion over a second catalytic agent in like manner andremoving after each catalytic agent the ammonia ,formed by each passageover said catalytic agents and replacing the ammonia formed and removedby I fresh hydrogen and nitrogen supplied tofirst catalytic agent.

4. The process of producing ammoniaby, passing a mixture of hydrogen andnitrogen, after heat exchange with the gases of reaction and at elevatedtemperature and pressure, over a catalytic agent andremoving at lowertemperature the ammonia formed, then again passing a pot:-

' tion of the residual gasesover the same catalytic agent, whilerepeatedly passing the remaining portion over a second catalytic agentin like manner and removing after each catalytic agent the ammoniaformed'by eachpassage over said catalytic agents and replacing theammonia formed. and removed by resh hydrogenand nitrogen supplied tofirst ca alytic agent, and while starting the reaction by electricmeans. i

5. The process of producing ammonia, by passing a mixture of hydrogenand nitrogen mixed in suitable proportions, at elevated temperature andpressure, over a catalytic agent andremoving at lower temperature theammonia formed then again passing a. portion of the. residual gases.

' over the same catalytic agent while repeatedly passing the remainingportion over a second catalytic agent, removifigmt lower temperature theammonia formed by each passage of gases over,

said catalytic agent and purging continuously after said secondcatalytic agent after the ammonia has been removed while replacing theammonia formed and the gases purged with fresh hydrogen and nitrogensupplied to the first of said catalytic agents and while passing theincoming gases in heat exchange with the outgoing gases from each ofsaid catalytic agents.

6. The process of producing ammonia by passing a mixture of hydrogen andnitrogen mixed in suitable proportions, at elevated temperature andpressure, over a catalytic agent and removing at lower temperature theammonia formed then again passing a portion of the residual gases overthe same catalytic agent while repeatedly passing the remaining portionover a second catalytic agent, removing at lower temperature the ammoniaformed by each passage of gases over said catalytic agent and purgingafter said second catalytic agent after the ammonia has been removedwhile replacing the ammonia formed and the gases purged with freshhydrogen and nitrogen supplied to the first of said catalytic agents andwhile passing the incoming gases in "heat exchange with the outgoinggases from each of said catalytic agents and while starting the reactionby electric means.

7. The process of producing ammonia by passing a mixture of hydrogen andnitrogen at elevated temperature and pressure over a catalytic body andremoving at lower temperature the ammonia formed then again passing, aportion of the residual gases over the same catalyst and repeatedlypassing the remaining portion at increased pressure over a secondseparate catalytic body and removing the ammonia formed then purgingafter said second catalytic body, while replacing the ammonia formed andgases purged with fresh hydrogen and nitrogen supplied to firstcatalytic body, and while passing the ingoing gases in heat exchangewith. the outgoing gases from each of saidcatalytic bodies.

8. The process of producing ammonia by passing a mixture of hydrogen andnitrogen at elevated temperature and pressure over a catalytic agent,then removing, at lower temperature, the

ammonia formed, then again passing a portion of the residual gases overthe same catalyst and passing the remaining portion over a secondcatalyst, then removing, at lower temperature,'the ammonia formed, thenpurging all the residual gases leaving said second catalyst whilereplacing the ammonia formed and the gases purged with fresh hydrogenand nitrogen supplied to first catalytic agent and while passing theingoing gases in heat exchange with the outgoing gases from each of saidcatalytic agents.

9. The process-ofproducing ammonia by passing a mixtureof hydrogen andnitrogen at elethen purging all the-residual fgases. leaving saidsecondcatalytic body, after the removal of ammonia while replacing the ammoniaformed and gases purged with fresh hydrogen and nitrogen supplied tofirst catalytic body and while passing the ingoing gases in heatexchange with the out going gases from each of said catalytic bodies.

10. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, at elevated temperature and pressure, over suitablecatalytic agents arranged in series and removing at lower temperature,after each catalytic agent, the ammonia formed, then again passing aportion of the residual gases over the same catalytic .agents whilerepeatedly passing another portion vatedtemperature and pressure, over apurifying catalytic mass then in contact with ammonia at loweredtemperature, then over a second catalytic agent then removing, at lowertemperature, the ammonia formed then again passing a portion of theresidual gases over the same catalysts and passing the remaining portionrepeatedly over a separate catalytic agent and removing the ammoniaformed with each passage over said catalytic agent while replacing theammonia formed with fresh hydrogen and nitrogen, supplied to thepurifying catalytic mass, and while passing the ingoing gases in heatexchange with the outgoing gases from each of said catalysts.

12. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, in suitable proportions at elevated temperature andpressure, over catalytic agents arranged in series and removing at lowertemperature; after each catalytic agent, the ammonia formed, then againpassing a portion of the residual gases overthe same catalytic agents,while repeatedly passing the remaining portion over another separatecatalytic agent in like manner, and'removing the ammonia formed by eachpassage ofgases over ,said separate catalytic agent and purgingcontinuously after said separate catalytic agents, after the ammonia hasbeen removed, while replacing the ammonia formed and gases purged withfresh hydrogen and nitrogen supplied to the first catalytic agent ofsaid series and while passing the ingoing gases in heat exchange withthe outgoing gases fromeach of said catalytic agents.

13. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, in suitable proportions at elevated temperature andpressure, over catalytic agents arranged in series and removing at lowertemperature, after each catalytic agent, the ammonia formed, then againpassing a portion of the residual gases over the same catalytic agents,while repeatedly passing the remaining. portion over another separatecatalytic agent in like manner, and removing the ammonia formed by eachpassage of gases over said separate catalytic agent and purging aftersaid separate catalytic agents, after the ammonia has been removed,while replacing the ammonia formed and gases purged with fresh hydrogenand nitrogen supplied to the first catalytic agent of said series andwhile passing the ingoing gases in heat exchange with the outgoing gasesfrom each of said catalytic agents and while starting the reaction byelectric means. 14. The process of producing ammonia by passing hydrogenand nitrogen, mixed in suitable proportion at elevated temperature andpressure, over catalytic agents arranged in series and removing at lowertemperature, after each catalyst, the ammonia formed, then againrecirculating a portion of the residual gases, over the same catalyticagents, and by-passing a portion of said recirculated gases to thesecond catalyst of said series and circulating repeatedly the remainingportion of said residual gases over another separate catalytic agent andremoving the ammonia formed, then purging after said separate catalyticagent, after the ammonia has been removed, while' replacing the ammoniaremoved and gases purged with fresh hydrogen and nitrogen supplied tothe first catalytic agent of said series and while passing the ingoinggases in heat exchange with the outgoing gases of each of said catalyticagents.

' 15. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, at elevated temperature and pressure, over suitablecatalytic agents, arranged in series, and removing at lower temperature,after each catalytic agent, the ammonia formed, then again passing theresidual gases over said catalytic agents and replacing the gasesremoved with fresh hydrogen and nitrogen supplied to the first catalyticagent of said series, said fresh hydrogen and nitrogen containing overone percent by volume of inert gases.

16. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, at elevated temperature and pressure, over suitablecatalytic agents arranged in series and removing, at lower temperature,after each catalytic agent, the ammonia formed, then again passing theresidual gases over said catalytic agents and replacing the gasesremoved with fresh hydrogen and nitrogen supplied to the first catalyticagent of said series, said fresh hydrogen and nitrogen containing overone percent by volume of inert gases, while passing the ingoing gases inheat exchange with the outgoing gases from each of said catalyticagents.

1'7. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, at elevated temperature and pressure, over suitablecatalytic agents, arranged in series, and removing at lower temperature,after each catalytic agent, the ammonia formed, then again passing theresidual gases over said catalytic agents and replacing the gasesremoved with fresh hydrogen and nitrogen supplied to the first catalyticagent of said series, said fresh hydrogen and nitrogen containing overone percent by volume of inert gases, while passing the ingoing gases inheat exchange with the outgoing gases, from each of said catalyticagents, and while purging after the last catalytic agent of the seriesand after the ammonia has been removed. i

18. The process of producing ammonia by passing a mixture of hydrogenand nitrogen, at elevated temperature and pressure, over suitablecatalytic agents, arranged in series, and removing at lower temperature,after each catalytic agent, the ammonia formed, then again passing theresidual gases over said catalytic agents and replacing the gasesremoved with fresh hydrogen and nitrogen supplied to the first catalyticagent of said series while passing the ingoing gases in heat exchangewith the outgoing-gases, from each of said catalytic agents, and whilepurging after the last catalytic agent of the series and tric parts andfrom the outer to the inner of said concentric parts.

20. The process of producing ammonia by the synthesis of .its elementsin the presence of a catalyst, which comprises passing a mixture ofhydrogen and nitrogen gas over a suitable catalytic body at an elevatedtemperature and pressure, said catalytic body being formed and dividedinto a plurality of concentric parts causing the gas to How in oppositedirectionsin each of said concentric parts and from the outer to theinner of said concentric parts, and while causing the cooler gasesentering the catalyst body to be heated through indirect heat exchangeby the hotter gases of reaction leaving said catalyst body.

21. The process of producing ammonia by the synthesis of its elements inthe presence of a catalyst, which comprises passing a mixture ofhydrogen and nitrogen gas over a suitable catalytic body at an elevatedtemperature and pressure, said catalytic body being formed and dividedinto a plurality of concentric parts causing the gas to flow in oppositedirections in each of said concentric parts and from the outer to theinnerof said concentric parts, and while causing the cooler gasesentering the catalyst body to be heated through indirect heat exchangeby the hotter gases of reaction leaving said catalyst body and whilestarting the reaction by electric means.

22. The process of producing ammonia by passing a gaseous mixture,containing hydrogen and nitrogen in suitable proportions at eleveatedtemperature' and pressure, over suitable catalyticagents arranged inseries and removing, at lower temperature after each catalytic agent,the ammonia formed, then again passing a portion of the residual gasesover the same catalytic agents while passing another portion overanother separate catalytic agent and removing the ammonia formed, thenpurging the residual gases after said removal of ammonia while passing,the ingoing gases in heat exchange with the outgoing gases from each ofsaid catalytic agents.

23. The process of producing ammonia by passing a gaseous mixture,containing hydrogen and nitrogen in suitable pro-portions at elevatedtemperature and pressure, over suitable catalytic agents arranged inseries and removing, at lower temperature after each catalytic agent,the ammonia formed, then again passing a portion of the residual gasesover the same catalytic agents while passing another portion atincreased pressure over a separate catalytic agent and removing theammonia formed, then purging the residual gases after said removal ofammonia after said separate catalytic agent.

24. The process of producing ammonia by passing a gaseous mixturecontaining hydrogen and nitrogen in suitable proportions at elevatedtemperature and pressure, over suitable catalytic agents arranged inseries and removing, at lower temperature after each catalytic agent,the ammonia formed, then again recirculating a portion of the residualgases over the same catalytic agents while circulating another portionof said residual gases at increased pressure over another separatecatalytic agent and removing the ammonia formed by each passage ofthe'gases over I said catalytic agent.

25. The process of producing ammonia by passing a gaseous mixture,containing hydrogen and nitrogen in suitable proportions at elevatedtemperature and pressure, over suitable catalytic agents arranged inseries and removing, at lower temperature after each catalytic agent,the ammonia formed, then again passing a portion of the residual gasesover the same catalytic agents while circulating another portion of saidresidual gases, at increased pressure, over another separate catalyticagent and removing the ammonia formed by each passage of gases over saidseparate catalytic agent and purging after the re-- moval of ammoniafollowing said separate catalytic agent and while passing the ingoinggases in heat exchange with the outgoing gases from each of saidcatalytic agents and replacing the gases converted to ammonia and thegases purged with a fresh gaseous mixture containing hydrogen andnitrogen.

26. The process of producing ammonia by passing a gaseous mixture,containing hydrogen and nitrogen in suitableproportions at elevatedtemperature and pressure, over a suitable catalytic agent and removingthe ammonia formed, then again passing a portion of the residual gasesover the same catalytic agent while passing another portion of saidresidual gases over another separate catalytic agent and removing theammonia formed and while replacing the gases removed by a fresh gaseousmixture containing hydrogen and nitrogen.

FORREST C. REED.

